The invention relates to a method for demounting a turbine blade according to the preamble of claim 1. The invention also relates to a device for applying the method.
In the demounting of turbine blades which are arranged in a groove on the rotor or on the stator of the thermal turbomachine, it is known from the prior art to demount these by means of a so-called expeller. This expeller, which is usually operated pneumatically and is also designated as a pneumatic hammer, engages on the root plate in the region of the profiled issue of the rear side of the turbine blade, in order to expel the latter out of the axial groove.
However, this type of demounting has various disadvantages. Since there is only a very small amount of space between two rows of moving blades, for example of a gas turbine, the expulsion tool can be applied to the root plate only at an unfavorable angle to the expulsion direction. The result of this is that demounting becomes correspondingly time-consuming and difficult, since the force component expelling the blade root out of the groove is very low. Due to deposits between the axial groove and the blade root, a high coefficient of friction prevails between the two parts, and this makes it even more difficult to remove the turbine blade. As a result of the unfavorable point of engagement for the introduction of force, a tilting moment is generated at the blade root and makes it very difficult or even possible to remove the turbine blade. The expulsion tool may also damage a protective layer which is present, if appropriate, and which is applied to the surface of the turbine blade, even though the tool is equipped at the blade contact point with a nylon covering with which an attempt is made to avoid damage of this kind.
The object of the invention is to avoid the disadvantages mentioned. The invention achieves the object of providing a device and a method which makes it possible to remove a turbine blade in a simplified way. Moments on the turbine blade are to be avoided or reduced to a minimum during demounting. A protective layer which is present, if appropriate, is not to be damaged during demounting.
According to the present invention, this object is further achieved when turbine blade is drawn out of the circumferential groove in the axial direction by means of a device which engages on the blade root of the turbine blade in an embodiment of the present invention.
Advantageously, the force is generated entirely in the axial direction, thus virtually eliminating a moment leading to tilting. Moreover, the time for demounting the turbine blades is markedly reduced in this way.
In a particular embodiment, the turbine blade is demounted by means of a hooked slide. The hooked slide is introduced into a gap located between the blade base and the groove bottom and is removed there by means of at least one hook which is anchored in at least one clearance at the blade root. If present, an existing cooling-air bore of the turbine blade may advantageously be used as a clearance.
A supporting slide advantageously serves additionally to secure the position of the hooked slide during demounting. The turbine blade can be drawn out by means of the hooked slide by a device which is operated hydraulically and which is supported on the rotor or stator on supports next to the hooked slide and the axial groove.
The method according to the invention is suitable, in particular, for the demounting of guide vanes or moving blades in gas turbines, steam turbines or compressors.
The invention also relates to a device for applying the demounting method according to the preamble of claim 8. The device is characterized in that the demounting device consists of a hydraulically operated piston generating a tensile force which acts in the axial direction and which can be transmitted to the blade root of the turbine blade in such a way that it is possible to demount the turbine blade, and, in addition, next to the blade root, on the rotor or stator, means are present which are connected to the hydraulically driven piston in such a way that, during the demounting of the turbine blade, they allow support with respect to the tensile force generated by the piston. In addition, a hooked or supporting slide may be present, which makes demounting possible.